Factorization of two-particle distributions in AMPT simulations of Pb-Pb collisions at $\mathbf{\sqrt{s_{\text{NN}}}} $ = 5.02 TeV

Abstract

The flow ansatz states that the single-particle distribution of a given event can be described in terms of the complex flow coefficients $V_n$. Multi-particle distributions can therefore be expressed as products of these single-particle coefficients; a property commonly referred to as factorization. The amplitudes and phases of the coefficients fluctuate from event to event, possibly breaking the factorization assumption for event-sample averaged multi-particle distributions. Furthermore, non-flow effects such as di-jets may also break the factorization assumption. The factorization breaking with respect to pseudorapidity $η$ provides insights into the fluctuations of the initial conditions of heavy ion collisions and can simultaneously be used to identify regions of the phase space which exhibit non-flow effects. These proceedings present a method to perform a factorization of the two-particle Fourier coefficients $V_{nΔ}(η_a, η_b)$ which is largely independent of detector effects. AMPT model calculations of Pb-Pb collisions at $\sqrt{s_{\text{NN}}} = 5.02$ TeV are used to identify the smallest $|Δη|$-gap necessary for the factorization assumption to hold. Furthermore, a possible $Δη$-dependent decorrelation effect in the simulated data is quantified using the empirical parameter $F_2^η$. The decorrelation effect observed in the AMPT calculations is compared to results by the CMS collaboration for Pb-Pb collisions at $\sqrt{s_{\text{NN}}} = 2.76$ TeV.